JP2001200392A - Plating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure the high intra-surface uniformity of a plating film thickness with a plating device which rotates a wafer. SOLUTION: The wafer 1 is mounted at a rotary terminal board (not shown in Figure) holding cathode electrodes 3, is immersed into a plating liquid so as to face anode electrodes (not shown in Figure) and rotates in the plating liquid. Shielding plates 5 for shielding the neighborhood of contact points 4 of the cathode electrodes are fastened to the cathode electrodes 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating apparatus, and more particularly to a plating apparatus suitable for manufacturing a semiconductor device having a wiring having a damascene structure.

[0002]

2. Description of the Related Art As semiconductor integrated circuits have become finer and higher in density, wiring widths have become extremely fine, less than 0.2 μm. Since the Al-based material, which has been widely used in the miniaturized wiring as described above, has a high wiring resistance and insufficient electromigration resistance, the wiring material has a lower specific resistance and a lower electromigration resistance as a wiring material. High Cu is being adopted. Thus,
Since a Cu film cannot be easily patterned by photolithography like an Al film, when Cu is used as a wiring material, a wiring is generally formed by a damascene method of embedding a wiring in an insulating film. .

FIG. 5 is a cross-sectional view in the order of steps showing an example of a method of forming a wiring by a damascene method. Hereinafter, a method of forming a wiring having a damascene structure will be briefly described with reference to FIG. A first layer wiring 102 is formed on a first interlayer insulating film 101 formed on a semiconductor substrate (not shown) [FIG.
(A)]. Next, a first buried insulating film 103 is deposited on the entire surface [FIG.
The insulating film on the first layer wiring 102 is removed by a lithing method (FIG. 5C). Next, the second interlayer insulating film 104
Is deposited, a via hole is formed on the first layer wiring, and then a barrier metal and Cu are deposited by a sputtering method or the like to form a first base metal layer 105 (FIG. 5D). Next, a first Cu plating layer 106 was formed by electrolytic plating [FIG.
(A)] After that, the C
The conductive plug 107 is formed leaving the u-plated layer [FIG. 5 (f)].

Next, a second buried insulating film 108 is formed, a wiring groove is formed in the second buried insulating film 108, and then a barrier metal and Cu are deposited by a sputtering method or the like to form a second base metal layer 109 [FIG. )]. After depositing the second Cu plating layer 110 by electrolytic plating [FIG. 5 (h)], the second layer wiring 111 is formed by leaving the Cu plating layer only in the wiring groove by CMP or the like [FIG. 5 (i)]. ]. As described above, when forming a wiring by the damascene method, the step of forming a base metal layer and forming a Cu plating layer thereon is one step.
Or multiple times.

FIG. 6 is a sectional view showing a schematic structure of a conventional Cu plating apparatus. The wafer 1 having the base metal layer 2 formed on the surface is mounted on the rotating terminal plate 6. A plurality of cathode electrodes 3 that are in contact with the underlying metal layer 2 on the wafer 1 at the contact points 4 and supply power thereto are planted on the rotating terminal plate 6. The rotating terminal plate 6 is placed on a plating tank 7 filled with a plating solution while holding the wafer 1. The plating solution in the plating tank 7 is supplied by a plating solution introduction pipe 8 and discharged out of the apparatus by a discharge pipe 9. An anode electrode 10 is arranged at a position facing the wafer 1 in the plating tank, and a rectifying plate 11 is provided between the anode electrode 10 and the wafer 1. Further, between the anode electrode 11 and the wafer 1, a shield plate 5A that covers a peripheral portion of the wafer 1 is provided.

FIG. 7 is a plan view of the wafer portion shown in FIG. 6 as viewed from below. In this figure, the same reference numerals as those used in FIG. 6 are used, and therefore duplicate explanations are omitted. However, as shown in FIG. 7, the shield plate 5A has a donut shape and Cover the part. The shield plate 5A is made of a dielectric material such as plastic and shields the vicinity of the contact portion between the cathode electrode and the underlying metal layer, so that an excessively thick plating film is formed near the contact portion with the cathode electrode where the electric field is concentrated. It is provided in order to prevent the situation.

[0007]

In the case of damascene wiring of a semiconductor integrated circuit, in-plane uniformity of wiring resistance is required. To this end, it is necessary to ensure in-plane uniformity of Cu wiring film thickness after CMP. Therefore, it is desired to improve the in-plane film thickness uniformity of the Cu plating film which is a pre-process of CMP. However, the conventional plating apparatus described above cannot ensure sufficient in-plane uniformity of plating film thickness. The reason will be described below.

FIG. 8 is a view schematically showing equipotential lines appearing on the surface of the underlying metal layer 2 during plating film formation. During the plating film formation, as shown in FIG. 8, on the surface of the base metal layer 2, the base metal layer has a potential distribution in which the contact point 4 between the cathode electrode and the base metal layer has a maximum value. This is because the electrical resistance of the underlying metal layer 2 causes a voltage drop substantially proportional to the distance from the contact point 4. Thus, in an electric field having a uniform current density, the deposition rate at each point on the base metal layer 2 depends on the potential at that position, and the deposition rate is higher at a lower potential. Therefore, as the position is closer to the contact point 4, the film forming rate is larger and the film thickness is larger.

Therefore, in the conventional example, the anode electrode
Although the shield plate 5A is arranged between the wafers to reduce the deviation of the film formation rate due to the deviation of the potential distribution, in the conventional example, the shield plate 5A is fixed to the plating tank side.
I had to make it a donut shape. Therefore, point A having a low potential is shielded, but point B where the potential is not sufficiently high is not shielded, and a thick plating film is formed here. In addition, point C is shielded in spite of the sufficiently high potential, so that the film thickness becomes insufficient. In the case where the opening of the shield plate is narrowed to reduce the film thickness at the point B so as to cover the point B as well,
Since the point D having a high potential is also shielded, the region where the film thickness is insufficient expands. An object of the present invention is to solve the above-mentioned problems of the conventional technique, and an object of the present invention is to enable a plating layer to be formed with high in-plane uniformity on a rotating wafer.

[0010]

To achieve the above object, according to the present invention, there is provided a plating tank containing a plating solution,
A rotatable rotary terminal plate that holds the wafer so that at least the wafer surface is in contact with the plating solution, and a plurality of cathode electrodes that are held by the rotary terminal plate and contact the wafer to supply power thereto. A plating apparatus comprising: an anode electrode disposed in the plating solution so as to face the rotating terminal plate; and a shield plate provided to shield a contact point between a wafer and the cathode electrode and a peripheral portion thereof. Wherein the shield plate is fixed to the rotating terminal plate or the cathode electrode. Preferably, an opening or a slit is formed in the inner peripheral portion of the shield plate along the outer peripheral edge.

[Operation] According to the present invention, the shield plate for shielding the plating film-forming surface from the anode electrode is fixed on the rotating terminal plate for holding the cathode electrode or the wafer. For this reason, the vicinity of the contact point of the cathode electrode is intensively shielded and unnecessary portions need not be shielded, so that the in-plane uniformity of the plating film thickness can be improved. Further, when an opening or a slit is provided on the inner peripheral portion of the shield plate, the uniformity of the plating film thickness can be further improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a bottom view and a sectional view showing the vicinity of a cathode electrode after wafer loading, showing a first embodiment of the present invention. The entire configuration of the plating apparatus is the same as that of the conventional example shown in FIG. 6 except for the configuration of the shield plate 5.

On the wafer 1, an underlying metal layer 2 including a conductive Cu layer is formed by a sputtering method or the like in order to give a potential necessary for depositing Cu. As shown, when the wafer 1 is loaded into the Cu plating apparatus of the present embodiment, the four cathode electrodes 3 contact the underlying metal layer 2 at the contact points 4 respectively. Cathode electrode 3
Is usually formed of Pt, Ti, or the like in consideration of resistance to a Cu plating solution, conductivity, and stability. Shield plates 5 extending in a plane parallel to the wafer 1 and concentrically spread are fixed to the respective cathode electrodes 3 starting from positions that are separated from the respective contact points 4 by a certain distance in the vertical direction with respect to the wafer 1.

The extent of the spread of the shield plate 5 at which the in-plane film thickness distribution of the Cu plating film is optimal varies depending on film forming conditions such as the electrode-to-electrode distance unique to the Cu plating apparatus and the current density according to the process used. Therefore, it is desirable that shield plates of a plurality of sizes be prepared so as to be exchangeable. However, since the portion that does not overlap with the wafer 1 when viewed from the vertical direction of the wafer 1 plane hardly contributes to the film formation rate on the wafer, the shield plate 5 does not need to spread outside the wafer. . The material of the shield plate 5 is desirably a nonmetal such as polypropylene or vinyl chloride which has chemical resistance and does not cause precipitation of Cu.

FIG. 2 is a bottom view and a sectional view showing the vicinity of a cathode electrode after wafer loading, showing a second embodiment of the present invention. In FIG. 2, the same reference numerals are given to the same parts as those of the first embodiment shown in FIG.
Duplicate description will be omitted. The first embodiment shown in FIG.
The point different from the embodiment of the present invention is that the number of cathode electrodes 3 is four to eight.
The point is that the number of books increases, and the peripheral portion of the wafer 1 is completely shielded by the shield plate 5. According to this embodiment, since the number of cathode electrodes is increased, the deviation of the potential on the underlying metal layer 2 can be reduced, and the deviation of the plating film thickness can be reduced accordingly.
In addition, the entire periphery of the wafer is shielded,
In addition to expecting the same effects as in the first embodiment, it is also possible to simultaneously prevent the current density from being concentrated on the outer peripheral portion of the wafer 1, and to obtain a better film thickness in-plane distribution.

FIG. 3 is a bottom view showing the vicinity of a cathode electrode after wafer loading according to a third embodiment of the present invention. FIG.
In FIG. 7, the same reference numerals are given to the same parts as those of the first embodiment shown in FIG. 1, and the duplicate description will be omitted. The difference between the present embodiment and the first embodiment shown in FIG. 1 is that the shield plate 5 is a single continuous plate to shield the peripheral portion of the wafer 1 without a break. This is a point where a plurality of openings 5 a are formed at points away from the contact points 4 of the plate 5. According to the present embodiment,
By completely shielding the peripheral portion of the wafer, it is possible to simultaneously prevent the current density from being concentrated on the outer peripheral portion of the wafer 1 as in the second embodiment. In addition, the provision of the openings 5a in the shield plate 5 makes it possible to more accurately equalize the current density and to further improve the in-plane uniformity of the plating film thickness.

In the illustrated example, the opening 5a is formed so that the density increases as the distance from the contact point 4 increases, but the diameter of the opening farther from the contact point 4 is increased by keeping the density of the openings the same. You may do so. Instead of forming the opening, one or more concentric slits centered on the contact point may be formed. When a plurality of slits are formed, it is preferable to increase the width of the slit as the distance from the contact point 4 increases.

FIG. 4 is a bottom view and a sectional view showing the vicinity of a cathode electrode after wafer loading, showing a fourth embodiment of the present invention. In FIG. 4, the same parts as those of the first embodiment shown in FIG.
Duplicate description will be omitted. The first embodiment shown in FIG.
The difference from this embodiment is that a shield plate 5A fixed to a plating tank is added between an anode electrode (not shown) and a cathode electrode 3. According to the present embodiment, it is possible to shield the entire peripheral portion of the wafer with the added shield plate 5A, and the current density generated on the outer peripheral portion of the wafer 1 as in the second and third embodiments. Concentration can be prevented at the same time. Further, since the cathode electrode 3 is shielded, it is possible to suppress plating film formation on the cathode electrode.

While the preferred embodiment has been described above,
The present invention is not limited to these embodiments, and appropriate changes can be made without departing from the scope of the present invention. For example, in the embodiment, the shield plate is fixed near the contact point of the cathode electrode, but may be fixed to the horizontal portion of the cathode electrode. Further, instead of being fixed to the cathode electrode, it may be fixed to a rotating terminal plate. Further, although the description has been made on the assumption that the rotary terminal plate is not completely immersed in the plating solution, it may be completely immersed in the plating solution.

[0020]

As described above, in the plating apparatus according to the present invention, the shield plate for shielding the vicinity of the contact point with the cathode electrode on the wafer is fixed to the cathode electrode or the rotating terminal plate. Therefore, even in a plating apparatus in which the wafer rotates, only the vicinity of the contact point with the cathode electrode of the wafer can be intensively shielded, and the film thickness near the contact point can be prevented from becoming excessive. Becomes At the same time, it is possible to prevent a region where the plating film thickness is insufficient due to shielding unnecessary portions from being shielded, thereby improving the in-plane uniformity of the plating film thickness.

[Brief description of the drawings]

FIG. 1 is a bottom view and a cross-sectional view near a cathode electrode showing a first embodiment of the present invention.

FIGS. 2A and 2B are a bottom view and a sectional view near a cathode electrode showing a second embodiment of the present invention. FIGS.

FIG. 3 is a bottom view showing the vicinity of a cathode electrode according to a third embodiment of the present invention.

FIG. 4 is a bottom view and a sectional view near a cathode electrode showing a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view in a process order for describing a method of forming a wiring having a damascene structure.

FIG. 6 is a sectional view of a conventional plating apparatus having a rotating terminal plate.

FIG. 7 is a bottom view of the vicinity of a conventional cathode electrode.

FIG. 8 is a view showing equipotential lines appearing in a base metal layer on a wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 2 Base metal layer 3 Cathode electrode 4 Contact point 5, 5A Shield plate 5a Opening 6 Rotating terminal plate 7 Plating tank 8 Plating solution introduction tube 9 Discharge tube 10 Anode electrode 11 Rectifying plate 101 First interlayer insulating film 102 First layer Wiring 103 First embedded insulating film 104 Second interlayer insulating film 105 First underlying metal layer 106 First Cu plating layer 107 Conductive plug 108 Second embedded insulating film 109 Second underlying metal layer 110 Second Cu plating layer 111 Second layer wiring

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C25D 17/12 C25D 17/12 Z 21/10 302 21/10 302 21/12 21/12 A H01L 21 / 288 H01L 21/288 E

Claims (11)

[Claims] 1. A plating tank containing a plating solution, a rotatable rotary terminal plate for holding a wafer so that at least the wafer surface is in contact with the plating solution, and a rotatable terminal plate held by the rotary terminal plate and in contact with the wafer. A plurality of cathode electrodes for supplying power thereto, an anode electrode arranged in the plating solution facing the rotating terminal plate, a contact point between the wafer and the cathode electrode and a peripheral portion thereof. A shield plate provided so as to shield, wherein the shield plate is fixed to the rotating terminal plate or the cathode electrode. 2. A cathode according to claim 1, wherein said cathode electrode has a vertical hanging portion extending perpendicularly from said rotating terminal plate, a horizontal extending portion extending from a tip of said vertical hanging portion parallel to said rotating terminal plate toward a central portion thereof, A vertical upright portion extending vertically from the tip of the horizontal extending portion toward the rotary terminal plate,
2. The plating apparatus according to claim 1, wherein the shield plate is fixed to the horizontal extending portion or the vertical upright portion of the cathode electrode. 3. A part of the outer shape of the shield plate has a circular arc shape centered on a contact point between the cathode electrode and the wafer.
The plating apparatus described in the above. 4. The apparatus according to claim 1, wherein the shield plate is provided independently for each of the cathode electrodes.
4. The plating apparatus according to 2 or 3. 5. The plating apparatus according to claim 1, wherein the shield plate is provided as a single plate common to all the cathode electrodes. 6. The plating apparatus according to claim 1, wherein the shield plate has an opening or a slit formed at a position far from a contact point between the cathode electrode and the wafer. 7. A plurality of openings are formed in the shield plate, and the density of the openings increases or the diameter of the openings increases as the distance from the contact point between the cathode electrode and the wafer increases. The plating apparatus according to claim 1. 8. The shield plate has a plurality of slits formed concentrically around a contact point between the cathode electrode and the wafer, and a width of the slit is determined from a contact point between the cathode electrode and the wafer. The plating apparatus according to any one of claims 1 to 5, wherein the distance increases as the distance increases. 9. The plating apparatus according to claim 1, wherein the shield plate is provided so as to shield at least the entire periphery of the wafer. 10. The plating apparatus according to claim 1, wherein the shield plate is detachably attached to the rotary terminal plate or the cathode electrode. 11. A fixed shield plate fixed to the plating tank side, which shields an outer peripheral portion of the wafer, is arranged between the anode electrode and the cathode electrode. The plating apparatus according to any one of 1 to 10.